Quantum-State Homeostasis: A Source–Sink Architecture for Fault-Tolerant Logical Quantum Information An Open-System Information-Condensation Framework for Active Logical-State Maintenance

This paper addresses a missing architectural layer in fault-tolerant quantum computing. The central question is not whether quantum processors require cooling, better qubits, error-correcting codes, real-time decoders, protected oscillator modes, engineered reservoirs, or feedback, but whether these mechanisms can be organized into a single measurable condition for active logical-state maintenance. The paper proposes Quantum-State Homeostasis as a source–sink framework for stabilizing protected logical quantum information under continuous dissipation. In this framework, a fault-tolerant quantum processor is not modeled as a perfectly isolated object, nor as a collection of independent engineering patches. Instead, it is modeled as an engineered open-system information architecture whose logical state survives only when restoration capacity, basis sharpness, dominant protected-mode occupation, and entropy-export coupling close together. The central contribution is the homeostasis score Qhomeo. This score combines four necessary factors: restoration capacity above coherence-window load, sharply selected logical basis, dominant protected logical-mode occupation, and engineered source–sink coupling. The resulting condition, Qhomeo = Θ((RQτQ/IQ) − 1) · WQ · p0,Q · κQ, defines logical stability as a conjunctive architecture rather than a single hardware parameter. Cryogenic cooling may extend the coherence window τQ; quantum error correction and decoding may increase restoration capacity RQ; cat qubits, bosonic codes, surface codes, and protected oscillator manifolds may support WQ and p0,Q; reservoir engineering, leakage reset, syndrome extraction, ancilla reset, and feedback may close κQ. However, none of these mechanisms is sufficient alone. A colder processor can still fail if its logical basis is diffuse. A fast decoder can still fail if feedback is not effectively coupled. A protected code manifold can still fail if entropy cannot leave the protected subsystem. The paper therefore reframes fault tolerance as active homeostatic maintenance of a protected logical mode. The structural theorem of the paper is conditional: if a quantum-stabilization architecture admits operational definitions of restoration capacity, coherence window, protected information load, basis sharpness, dominant protected-mode occupation, and source–sink coupling, then it admits a Qhomeo representation. Under the reduced-order assumptions stated in the manuscript, the protected logical mode follows an attractor-like stability condition αΦ > Γ. The paper interprets this not as a new fundamental law of quantum mechanics, but as a reduced-order architectural description of logical survival. Quantum error correction is therefore understood as controlled information transfer: error entropy is not annihilated, but routed into syndrome records, reset costs, reservoir excitations, heat, leakage-removal pathways, or correction-frame updates while the protected logical state is preserved. The empirical layer is framed as an architectural consistency program rather than proof of completed fault tolerance. The framework is anchored against published results across cat-qubit, GKP, and neutral-atom platforms, showing that heterogeneous stabilization mechanisms can be interpreted through the same reduced-order source–sink structure. The paper further commits to time-bounded prospective predictions for next-generation dissipative cat experiments, GKP fixed-point relationships, neutral-atom code-distance scaling, and an engineering sweet-spot range for αΦ/Γ. Failure of individual predictions revises the corresponding sub-claim; failure of multiple predictions triggers broader re-evaluation of the framework. The manuscript also defines claim boundaries: Qhomeo does not replace Hamiltonian models, Lindblad equations, threshold proofs, or platform-specific noise models; it organizes them architecturally. It does not claim that a fault-tolerant quantum computer has already been built, that quantum processors are biological or conscious, or that cooling is unnecessary. Its value lies in proposing a falsifiable, platform-neutral, source–sink architecture for testing whether logical quantum information can be actively maintained as a protected, sharply selected, entropy-exporting dominant mode. Keywords: quantum error correction, fault tolerance, logical qubits, quantum-state homeostasis, Qhomeo, source-sink architecture, reservoir engineering, autonomous QEC, bosonic codes, cat qubits, GKP codes, neutral atoms, logical information condensate, protected logical mode, entropy exhaust, reduced-order model, architectural stability score, quantum information stabilization, prospective falsification.